Process and apparatus for preparing materials in an air furnace



Jan. 6, 1970 [KEN ET AL s,4ss,mo

PROCESS AND APPARATUS FOR PREPARING MATERIALS IN AN AIR FURNACE Filed Oct. 10, 1967 United States Patent U.S. Cl. 263-33 Claims ABSTRACT OF THE DISCLOSURE Cement and other materials are prepared in an air furnace, such as a rotary kiln into which a torch introduces a fuel-air-gas mixture and a lance supplies oxygen between the hot layer and the torch in such a manner that after hitting the layer it is deflected into the torch flame. In addition to the deflected oxygen stream, a further oxygen stream is directed parallel to the furnace axis or the flame and into contact with the flame.

BACKGROUND OF THE INVENTION German patent application M 69,713 relates to a process for the preparation of cement and other materials in an air furnace, particularly a rotary kiln, with a torch extending into the discharge end thereof for the introduction of a fuel-air-gas mixture and with a lance supplying an oxygen stream to the space between torch and layer of material. At least one oxygen stream is directed to the hot layer of material in such a manner that after hitting the layer it is deflected by it and is blown as an oxygen stream, against the torch flame.

In the preparation of cement in the rotary kiln, itis known to add oxygen to the flame to increase the flame temperature. This flame, radiating also to the roof arch, however, also affects the furnace lining. For avoiding this disadvantage, in a known process, the oxygen is blown in the longitudinal direction of the furnace and between flame and the bulk material. This causes the flame to become considerably hotter at the side facing the bulk material because of the blown-in oxygen, while the flame facing the roof arch remains relatively cool. This process has the disadvantage, however, that because of the type of oxygen nozzle position, the development of the flame (flame length, flame development, position of the hot flame zone) is variable within limits.

The above-noted German patent application discloses a process wherein the oxygen is undershot into the furnace and is first guided to the hot bulk material, In such a manner the oxygen, supplied to the furnace cold, is heated by the hot bulk material and then reaches the flame as a diffused cloud. Thereby a considerable part of the heat of the bulk material is absorbed from the oxygen and again conducted to the calcining process as additional heat energy. By changing the blowing angle, the flame length, the flame formation and the position of the hot zone of flame, can be regulated in a simple manner.

A regulation of the flame formation, the flame length and the position of the hot zone of flame in the known process encounters, however, certain difliculties. A main difliculty is that the cold oxygen stream can hardly influence the hot flame which is very stable because of its greater tenacity. The process according to the above-noted German patent application can be employed in furnaces of normal or oversize length with certain success. Indeed, the tenacity of the oxygen is increased by being heated by the hot material, but on the other hand its kinetic energy is intensely decreased by the diffusion effect on the material. The effect of the flame by the oxygen stream is therefore only possible at a certain and hardly regulatable distance from the furnace discharge end, even when the impact angle of the oxygen stream is changed by corresponding bending of the lance in such a manner that the flame and the oxygen cloud meet prematurely. This has the disadvantage that in rotary kilns of short over-all length, the combustion or sintering zones are set too far into the furnace and thus the other temperature zones are set too near the furnace input.

SUMMARY OF THE INVENTION The gist of the invention is therefore to eliminate the above-named disadvantages and to improve further the process of the above-noted German patent application.

According to the invention in addition to the deflected oxygen stream, there is simultaneously applied at least one other oxygen stream directed approximately parallel to the longitudinal axis of the furnace or the flame and touching or entering the flame. The oxygen can thus be supplied to the furnace undershot with a lance, where the lance can have two separated oxygen supply lines and oxygen nozzles. In the inventive process the flame can be formed in an advantageous manner entirely as desired. By variation of the amount of oxygen in the individual nozzles, by changing the oxygen blowing angle to the bulk material, and the oxygen discharge speed, the flame can be controlled as desired.

Furthermore, an advantage of the inventive process is in the changing during operation the flame position Without displacing the oxygen supply line, in such a manner that the furnace lining cannot be damaged by the hot flame constantly located on the same spot.

Advantageously a flame formation will then be possible when the oxygen stream, not diffused on the material prior to coming in contact with the flame, can mix with the hot oxygen stream diffused at the material and so increase its temperature and tenacity by indirect heat transfer from the material. The now hot and thus also tough oxygen stream is very suitable for flame formation and flame regulation and therefore offers a good possibility of controlling the temperature field.

Instead of oxygen, air or oxygen-enriched air can also be used.

In an advantageous further aspect of the invention, an air furnace is provided for the carrying out of the novel process, wherein the oxygen lance has several, but at least two, separate oxygen supply lines and oxygen nozzles. The oxygen passage of each nozzle can be individually controlled. The nozzles can be easily changed by screwing into the lance. It is suitable to make the nozzles movable by means of a joint so that the blowing angle to the bulk material can be varied.

THE DRAWINGS FIG. 1 shows a rotary kiln for the carrying out of the novel process; and

FIGS. 2-4 show the various arrangements for the admission of the flame with oxygen.

DETAILED DESCRIPTION The material 3 to be heated by flame 2 is located in the rotary kiln 1. Flame 2 is produced by torch 4 by means of coal dust, oil or gas together with air. Oxygen, air or oxygen-enriched air is blown into the flame through lance 5. Alternatively suitable solid, liquid or gaseous constituents can be mixed with the oxygen or other reactive gases, or gas mixtures can be used instead of oxygen. Lance 5 has two nozzles 6 and 7 for the formation of the air or oxygen streams 8 and 9, which are directed to the flame. Stream 8 runs approximately parallel to the longitudinal axis of the furnace or the flame and touches this underneath, while stream 9 is deflected to the underside of flame 2 over the surface of the melting or loose material 3.

If the nozzle 7 is made to be movable, then, in a simple and advantageous manner, a regulation of the flame is possible. FIGS. 2-4, for example, show the various adjustments of nozzle 7. The stream 9 deflected by the melting of loose material 3 can then be adjusted corresponding to the particular flame length, so that the most advantageous operating requirements can always be achieved. These are especially present when the straight oxygen stream 8 prior to coming in contact with flame 2 can be mixed with the hot oxygen stream 9 diffused at material 3 and thus its temperature and tenacity increase by indirect heat transfer from the material. The now hotter and thus also more tenacious oxygen stream is well suited for flame formation and flame regulation and therefore offers a good possibility of controlling the temperature field in furnace 1.

Of course, the invention is in no way limited to the embodiment described above and illustrated in the drawing. Furthermore, many deviations are feasible, particularly in the arrangement and construction of lance 5, in the choice of the number of nozzles, as well as their adjustment, without thereby deviating from the scope of the invention. Thus, the novel process can be used, for example, for the preparation and treating of other materials than cement, which can be both solid as well as liquid. Instead of a rotary kiln, other air furnaces can be used for the carrying out of the novel process which can also operate discontinuously in the batch process.

What is claimed is:

1. In a process for preparing materials in an air furnace into which a torch extends and introduces a flame from a fuel-air-gas mixture and two oxygen-containing gas streams are directed between the material in the furnace and the torch, whereby one stream is directed against the hot layer of material and then deflected by the layer into the flame and the other is directed substantially parallel to the longitudinal axis of the furnace and into contact with the flame.

2. The process of claim 1 wherein the gas is pure oxygen.

3. The process of claim 1 wherein the gas is air containing oxygen.

4. The process of claim 1 wherein the additional stream of oxygen containing gas mixes with the deflected stream before contacting the flame.

5. The process of claim 1 wherein the layer of material is at least partially oxidized upon contact with the oxygen containing gas.

6. The process of claim 1 wherein the gas is air enriched with oxygen.

7. In an apparatus for preparing materials including a rotary kilm having a discharge end with the material to be prepared flowing therethrough, a torch in said discharge end directing a flame therein, an oxygen supplying lance for directing an oxygen containing gas into the material and deflecting the gas into the flame, characterized by additional oxygen supply means directing at least one oxygen containing gas stream substantially parallel to the longitudinal axis of said furnace and into contact with the torch flame.

8. The apparatus of claim 7 wherein said lance and said supply means are individually adjustable.

9. The apparatus of claim 7 wherein said lance includes a nozzle for supplying the deflected gas stream, said supply means being a further nozzle on said lance, and said nozzles being removably screwed to said lance.

10. The apparatus of claim 8 including joint means for moving said nozzles to vary the gas streams therefrom.

References Cited UNITED STATES PATENTS 797,506 8/1905 'Eldred 26333 860,685 7/ 1907 Morgan 263-33 2,584,808 2/1952 Newhouse 26333 X 3,074,707 1/1963 Humphries et al. 26333 X JOHN J. CAMBY, Primary Examiner U.S. Cl. X.R. 263-52 

